Re: Gum pigments
Patrick Ravines (ravines@bwc.org)
Thu, 28 Apr 94 11:10:34 IDT
Olivo asks:
>I'd like to understand this better. How are acrylics and gouaches made up?
>What is the carrier and what is the pigment (I presume that the pigments are
>the same sort of stuf for all media, but may be wrong).
>
>As I understand it, the ideal pigmentation for Gum prints is a suspension of a
>coloured powder in the gum emulsion- since watercolours in a tube are
>effectively coloured powder mixed with gum, they are an obvious candidate.
>
>Anybody can tell me about the differences between media?
>
>Thanks
>Olivo
F...........................................................................M.....................................................M.{*
You are on the right track. I hope the stuff below helps ...
Pigments are finely powdered coloring materials used in making paint,
printing ink, and many other substances. Pigments are insoluble in the
"liquid vehicle" (or carrier or binder) with which it is mixed and the color
is a result of the mix being spread over a surface.
Pigments are ususally classified according to its origin for example "earth
colors" are those made by processing colored earths such as red iron oxides,
etc.
Pigments are one class of coloring materials. Others are dyes and lakes.
The "liquid vehicles" (I like this term, it makes me think of amourphous
jelly cars, buses ...) is the liquid used to disperse the pigments. Some are
oils, polymers (acrylics) and naturally occuring gums such as gum arabic, gum
tragacanth, etc. (By the way, gum arabic is also used in the food and
pharmaceutical industries as a filler. Next time you buy canned or prepared
foods look at the contents label, you may find it.)
Gouache colors, sold in tubes, contain the same ingredients as transparent
watercolors, {\"but{\ chalk is added to some of the duller pigments to brighten
them. For gouache and watercolors the pigments are dispersed in gum arabic.
Acrylic polymer colors are pigments dispersed in an acrylic polymer resin.
For gum printing you need to use gum arabic, a pigment, a dichromate salt
and light.
patrick
ravines@bwc.org